This investigation is part of an overall objective of studying the response of the whole body to acid-base alterations. The term "whole body" in this context implies intracellular as well as extracellular fluids in the living state. Since these responses change with time they must be studied in relation to duration of altered acid-base state. Intracellular compensation to chronic hypercapnia will be studied in rats held for various periods of time in an environmental chamber in which a constant elevated PCO2 can be maintained. Intracellular response to hemorrhagic shock and to salicylate intoxication will be studied in dogs. Analyses of skeletal muscle, cardiac muscle, and brain will be carried out. Intracellular pH will be determined by the C14 DMO method.